Many electronic and input devices include a touch-sensitive surface for receiving user inputs. Devices such as smart telephones, tablet computing devices, laptop computers, track pads, wearable communication and health devices, navigation devices, and kiosks can include a touch-sensitive surface. In some cases, the touch sensitive surface is integrated with a display to form a touch-screen or touch-sensitive display.
The touch-sensitive surface may detect and relay the location of one or more user touches, which may be interpreted by the electronic device as a command or a gesture. In one example, the touch input may be used to interact with a graphical user interface presented on the display of the device. In another example, the touch input may be relayed to an application program operating on a computer system to affect changes to the application program.
Touch sensitive surfaces, however, are limited to providing only the location of one or more touch events. Moreover, touch, like many present inputs for computing devices, is binary. The touch is either present or it is not. Binary inputs are inherently limited insofar as they can only occupy two states (present or absent, on or off, and so on). In many examples, it may be advantageous to also detect and measure the force of a touch that is applied to a surface. In addition, if the force can be measured across a continuum of values, it can function as a non-binary input. Further, incorporating a touch sensing device and a force sensing device with the display of an electronic device may provide an enhanced user input for controlling an application or function of the electronic device as compared to using a touch sensor alone.
One challenge with incorporating a force sensing device into the display of an electronic device is that signals associated with the display and other components in the electronic device can introduce noise into the force signals produced by the force sensing device. The noise can cause errors in the force measurements. Additionally, the noise produced by the display and other components can overwhelm the force signals in that the magnitude of the noise can be much greater than the magnitude of the force signals, making it difficult to discern the force signals from the noise.